The present invention refers to a light beam projector comprising a light source and a reflecting means, which are arranged for converging the light generated by the light source into a light beam, such reflecting means having a hollow curved surface and a focal point located where the light source is positioned, means for filtering the light beam, able to change its colour based on the angle of incidence of the beam on them, said filtering means comprising a plurality of filters arranged by sectors to form a diaphragm interposed between the light source and the light beam output from the projector, where said sectors, in order to change the angle of incidence of the light beam on the filters, can rotate on their own axis, to move from a closed position where they fully intercept the light beam, to an open position where such a light beam is not intercepted, as well as to all intermediate positions.
In particular, the present invention refers to light beam projectors for medium, high and very high lighting power.
According to the state of the art, several methods are known for changing the colour of the light beam emitted by a source of light. Many systems use coloured gel interposed in the light beam for changing its colour and, additionally, they make use of various mechanical techniques for changing different coloured gel associated to a single lighting device.
However, these systems have considerable drawbacks, since they do not ensure continuous colour corrections nor obtaining small changes to the above corrections.
Other recent systems have improved the system for changing the colour of the light beam, using dichroic filters instead of coloured gel.
These filters are formed by a plurality of layers, which may have a low or high refraction index, alternatively. According to the type and number of the layers of a filter, the latter takes a basic coloration, such as magenta, cyan, yellow, etc.
In the state of the art, it is also known that such dichroic filters have very peculiar features, since they operate on an interference principle, i.e. substantially separating two colours from a white light source, one of these colours being transferred and the other colour complementary to the first one, being reflected.
Moreover, changing the angle of incidence (reference is made to the patent U.S. Pat. No. 3,085,468) of a light beam with respect to a dichroic filter, the colour spectrum (i.e. the wavelength of the coloured light) transmitted through the filter can be changed, i.e. changing the colour of the light beam exiting the filter.
A problem frequently arising when using the above means for changing the colour of the light beam, in particular when high power systems are concerned, is caused by overheating of the equipment inside the lighting systems. Quite often, in fact, free air circulation is not allowed inside them; additionally, the light not being transmitted, i.e. reflected by the filters, will directly affect the lamp and other internal components of the equipment, overheating these components.
Another problem associated to the known systems is that only one colour shade of the light beam emitted by the system can be obtained each time. These systems, in fact, generally use diaphragms with dichroic filters, which are so arranged to be intercepted by a light beam, where the dichroic filters of each diaphragm have the same features and have all the same angle of rotation to the direction of the light beam.
This causes a certain rigidity in selecting the light that can be obtained from said known devices.